This invention relates to an analgesic composition and method for alleviating pain. More particularly, this invention is concerned with alleviating pain by administering to a mammal exhibiting pain (a) an analgesia-effective amount of at least one narcotic agonist-antagonist analgesic; and, (b) a narcotic agonist-antagonist analgesic-potentiating amount of at least one nontoxic antagonist, or blocker, for the N-methyl-D-aspartate (NMDA) receptor.
Narcotic agonist-antagonist analgesics are known. In general, narcotic agonist-antagonist analgesics constitute a distinct subclass of opioids and are differentiated from the latter by their mixed actions, meaning, they are not full agonists at all opioid receptors, e.g., .mu., .delta., .kappa., etc. receptors. Instead, narcotic agonist-antagonist analgesics are believed to either exert their analgesic action by working as agonists at some opioid receptors and antagonists or very weak agonists at other opioid receptors, i.e., mixed narcotic agonist-antagonists, or exert their analgesic action by working as agonists at some opioid receptors, i.e., partial agonists. Mixed narcotic agonist-antagonist analgesics will typically be the combination of .mu. antagonism coupled with .kappa. agonism. Partial agonist analgesics will typically be .mu. agonism.
Heretofore, there has been no recognition or appreciation that the analgesic effectiveness of a narcotic agonist-antagonist analgesic can be appreciably potentiated, or enhanced, by administration of a narcotic agonist-antagonist analgesic prior to, with or following the administration of a narcotic agonist-antagonist analgesic-potentiating amount of a nontoxic NMDA receptor antagonist.